Zeta Trianguli Australis

Zeta Trianguli Australis (ζ TrA) is a spectroscopic binary in the constellation Triangulum Australe. It is approximately 39.5 light years from Earth.

Zeta Trianguli Australis
Observation data
Epoch J2000      Equinox J2000
Constellation Triangulum Australe
Right ascension 16h 28m 28.14362s[1]
Declination −70° 05′ 03.8419″[1]
Apparent magnitude (V) 4.90[2]
Characteristics
Spectral type F9 V[3]
U−B color index +0.02[2]
B−V color index +0.55[4]
Astrometry
Radial velocity (Rv)+8.3[5] km/s
Proper motion (μ) RA: 199.97[1] mas/yr
Dec.: 110.97[1] mas/yr
Parallax (π)82.53 ± 0.52 mas[1]
Distance39.5 ± 0.2 ly
(12.12 ± 0.08 pc)
Absolute magnitude (MV)4.49[6]
Orbit[7]
Period (P)12.97662 ± 0.00017 d
Eccentricity (e)0.01442 ± 0.00021
Periastron epoch (T)JD 2452752.31955
Argument of periastron (ω)
(secondary)		252.98° ± 0.80°
Semi-amplitude (K1)
(primary)		7.4988 ± 0.0016 km/s
Details
ζ TrA A
Mass1.12[8] M☉
Metallicity [Fe/H]–0.18[4] dex
Rotation13 days[4]
Rotational velocity (v sin i)3.23[9] km/s
Age600–900[10] Myr
ζ TrA B
Mass0.40[8] M☉
Other designations
CD -69°2558, FK5 610, GCTP 3719.00, Gl 624, HD 147584, HIP 80686, HR 6098, LTT 6558, SAO 253554.
Database references
SIMBADdata
ARICNSdata

The binary's composite spectral class is F9V and its combined apparent magnitude is +4.90. The pair orbit each other once every 13 days, and the orbital eccentricity is a low 0.014, making it nearly circular.[7]

Somewhat surprisingly for a star located at 70° S, it is a candidate swarm member of the Ursa Major moving group.[11] However, there is some evidence to the contrary.[4]

References
  1. van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752v1, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600. Note: see VizieR catalogue I/311.
  2. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data. SIMBAD, Bibcode:1986EgUBV........0M.
  3. Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637, S2CID 119476992.
  4. Maldonado, J.; et al. (October 2010), "A spectroscopy study of nearby late-type stars, possible members of stellar kinematic groups", Astronomy and Astrophysics, 521: A12, arXiv:1007.1132, Bibcode:2010A&A...521A..12M, doi:10.1051/0004-6361/201014948, S2CID 119209183.
  5. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
  6. Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191, S2CID 118577511.
  7. Skuljan, Jovan (2004), "Accurate orbital parameters for the bright southern spectroscopic binary ζ Trianguli Australis – an interesting case of a near-circular orbit", Monthly Notices of the Royal Astronomical Society, 352 (3): 975, Bibcode:2004MNRAS.352..975S, doi:10.1111/j.1365-2966.2004.07988.x.
  8. Tokovinin, Andrei (April 2014), "From Binaries to Multiples. II. Hierarchical Multiplicity of F and G Dwarfs", The Astronomical Journal, 147 (4): 14, arXiv:1401.6827, Bibcode:2014AJ....147...87T, doi:10.1088/0004-6256/147/4/87, S2CID 56066740, 87.
  9. Martínez-Arnáiz, R.; et al. (September 2010), "Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter", Astronomy and Astrophysics, 520: A79, arXiv:1002.4391, Bibcode:2010A&A...520A..79M, doi:10.1051/0004-6361/200913725, S2CID 43455849.
  10. Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008), "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics", The Astrophysical Journal, 687 (2): 1264–1293, arXiv:0807.1686, Bibcode:2008ApJ...687.1264M, doi:10.1086/591785, S2CID 27151456.
  11. Croswell, Ken (2005). "Descendants of the Dipper". Astronomy. 33 (3): 40–45. Bibcode:2005Ast....33c..40C. ISSN 0091-6358.


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